I know that melatonin hormone is released by the pineal gland upon the fall of the night, so we can go to sleep easier. But nowhere I could find how the daily release of this hormone is triggered in humans that live on the north pole or so, so the sun wouldn't go down for 6 months and then it would be dark for another six months. It assumes the existence of other stimulatory mechanisms for the daily melatonin release...

but at the same time us organisms will adapt to our surrounding enviroment.......your body will get on a set schedule......just as if you began to work a graveyard shift you have to learn to sleep through the daylight....your body will make what adjustments are needed to reach a homeostasis level